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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Experimental assessment of a computer program used in Space Shuttle orbiter entry heating analysis

A high temperature reusable surface insulation (HRSI) tile taken from the Space Shuttle orbiter was subjected to a nominal heating rate of 60 kW/sq m in the laboratory. The surface temperature response to this heating was measured and used as input to a computer program which computed the applied heating rate. The program is part of a software system that is used to infer convective heating rates to the orbiter thermal protection system during entry. The measured and computed heating rates are compared. Results confirm the applicability of this program to the determination of flight heat transfer rates from flight measured surface temperature data.

Wells, W. L.↗
NASA NTRS1983

A study of the influence of soil moisture on future precipitation

Forty years of precipitation and surface temperature data observed over 261 Local Climatic Data (LCD) stations in the Continental United States was utilized in a ground hydrology model to yield soil moisture time series at each station. A month-by-month soil moisture dataset was constructed for each year. The monthly precipitation was correlated with antecedent monthly precipitation, soil moisture and vapotranspiration separately. The maximum positive correlation is found to be in the drought prone western Great Plains region during the latter part of summer. There is also some negative correlation in coastal regions. The correlations between soil moisture and precipitation particularly in the latter part of summer, suggest that large scale droughts over extended periods may be partially maintained by the feedback influence of soil moisture on rainfall. In many other regions the lack of positive correlation shows that there is no simple answer such as higher land-surface evapotranspiration leads to more precipitation, and points out the complexity of the influence of soil moisture on the ensuring precipitation.

Fennessy, M. J.↗
NASA NTRS1983

Accretion onto magnetized neutron stars - X-ray pulsars with intermediate rotation rates

Assuming that the accreting material originates in a wind or envelope and therefore carried no net angular momentum, the Kevin-Helmholtz instability is applied to the transport of accreting plasma across the magnetopause of a rotating and magnetized neutron star for the case in which this surface is interchange-stable. Magnetopause location is determined, and the blackbody emission temperature is estimated. A possible period-dependence is noted in the X-ray temperature data which is in approximate agreement with the present model calculations. The magnetopause is found to be insufficiently stable to support an optically thick sheath of plasma surrounding the source, so that neither shrouding of the X-ray source nor significant reprocessing of the radiation field is possible in the model presented. It is concluded that while the flow structure at the magnetopause can control accretion column geometry, the emerging pulse profile and spectra are only indirectly altered, through a dynamical influence on emission region geometry.

Burnard, D. J.↗
NASA NTRS1983

Shock temperatures in anorthite glass

Temperatures of CaAl2Si2O8 (anorthite glass) shocked to pressures between 48 and 117 GPa were measured in the range from 2500 to 5600 K, using optical pyrometry techniques. The pressure dependence of the shock temperatures deviates significantly from predictions based on a single high pressure phase. At least three phase transitions, at pressures of about 55, 85, and 100 GPa and with transition energies of about 0.5 MJ/kg each (approximately 1.5 MJ/kg total) are required to explain the shock temperature data. The phase transition at 100 GPa can possibly be identified with the stishovite melting transition. Theoretical models of the time dependence of the thermal radiation from the shocked anorthite based on the geometry of the experiment and the absorptive properties of the shocked material yields good agreement with observations, indicating that it is not necessary to invoke intrinsic time dependences to explain the data in many cases.

Boslough, M. B.↗
NASA NTRS1984

Integration and flight demonstration of a high-capacity monogroove heat-pipe radiator

The cancellation of the TDRS-B satellite as the payload for the eighth Space Shuttle mission provided a unique opportunity to demonstrate on-orbit operation of the high-capacity monogroove heat pipe used in the space constructible radiator subsystem. In less than 4 months, a flight experiment was conceived, designed, fabricated, tested, integrated with a payload carrier, installed in the Orbiter Challenger payload bay, and successfully operated in flight. Still color photographs and direct crew visual observation of color changes in a pattern of temperature-sensitive liquid-crystal tapes provided the temperature data necessary to verify successful on-orbit startup and orbital transient response of the heat pipe when subjected to a heat load from its attached electrical heaters. This successful on-orbit demonstration verified analytical design tools and provided confidence in the use of high-capacity heat pipes for future space applications. The flight experiment hardware and the integration and test activities that led to the flight are described, and the actual flight results are compared to analytical performance predictions.

Rankin, J. G.↗
NASA NTRS1985

Calculation of pressure-broadened linewidths for CO in Ar

Calculations of the pressure-broadening cross sections of CO in Ar have been made within the infinite-order sudden (IOS) and coupled states (CS) quantum scattering approximations. Two intermolecular potentials were used, a pairwise additive atom-atom potential which has been employed previously in semiclassical (modified Anderson theory) studies of this system and one calculated ab initio within an electron gas formalism. Predictions from the two potentials generally agree within about 25 percent and bracket experimental values (except for some recent high temperature data obtained in shock tube experiments). The CS approximation appears to be quite accurate although computationally expensive. The much cheaper IOS approximation is accurate for the J = 0-1 line but does not properly predict the dependence on line number. The quantum results are also compared with earlier semiclassical values.

Green, S.↗
NASA NTRS1986

Estimating Microwave Delay by Atmospheric Water

Tropospheric path delays for microwave very-long-baseline interferometry (VLBI) estimated with algorithm that determines and explicitly integrates simple water-vapor distribution based on temperature data from water-vapor radiometer (WVR) and emission model. Although computationally complex, method readily accommodates even dramatic changes in observation conditions, emission model, and WVR equipment. Algorithm accommodates changes in observation conditions, emission model, and radiometer hardware.

Robinson, S. E.↗
NASA NTRS1983

Dynamic gas temperature measurement system

A gas temperature measurement system with compensated frequency response of 1 KHz and capability to operate in the exhaust of a gas turbine combustor was developed. Environmental guidelines for this measurement are presented, followed by a preliminary design of the selected measurement method. Transient thermal conduction effects were identified as important; a preliminary finite-element conduction model quantified the errors expected by neglecting conduction. A compensation method was developed to account for effects of conduction and convection. This method was verified in analog electrical simulations, and used to compensate dynamic temperature data from a laboratory combustor and a gas turbine engine. Detailed data compensations are presented. Analysis of error sources in the method were done to derive confidence levels for the compensated data.

Elmore, D. L.↗
NASA NTRS1985

SAGE aerosol measurements. Volume 1: February 21, 1979 to December 31, 1979

The Stratospheric Aerosol and Gas Experiment (SAGE) satellite system, launched on February 18, 1979, provides profiles of aerosol extinction, ozone concentration, and nitrogen dioxide concentration between about 80 N and 80 S. Zonal averages, separated into sunrise and sunset events, and seasonal averages of the aerosol extinction at 1.00 microns and 0.45 microns ratios of the aerosol extinction to the molecular extinction at 1.00 microns, and ratios of the aerosol extinction at 0.45 microns to the aerosol extinction at 1.00 microns are given. The averages for 1979 are shown in tables and in profile and contour plots (as a function of altitude and latitude). In addition, temperature data provided by the National Oceanic and Atmospheric Administration (NOAA) for the time and location of each SAGE measurement are averaged and shown in a similar format. Typical values of the peak aerosol extinction were 0.0001 to 0.0002 km at 1.00 microns depth values for the 1.00 microns channel varied between 0.001 and 0.002 over all latitudes.

Mccormick, M. P.↗
NASA NTRS1986

Burner liner thermal-structural load modeling

The software package Transfer Analysis Code to Interface Thermal/Structural Problems (TRANCITS) was developed. The TRANCITS code is used to interface temperature data between thermal and structural analytical models. The use of this transfer module allows the heat transfer analyst to select the thermal mesh density and thermal analysis code best suited to solve the thermal problem and gives the same freedoms to the stress analyst, without the efficiency penalties associated with common meshes and the accuracy penalties associated with the manual transfer of thermal data.

Maffeo, R.↗
NASA NTRS1986

Present state of knowledge of the upper atmosphere: An assessment report; processes that control ozone and other climatically important trace gases

The state of knowledge of the upper atmosphere was assessed as of January 1986. The physical, chemical, and radiative processes which control the spatial and temporal distribution of ozone in the atmosphere; the predicted magnitude of ozone perturbations and climate changes for a variety of trace gas scenarios; and the ozone and temperature data used to detect the presence or absence of a long term trend were discussed. This assessment report was written by a small group of NASA scientists, was peer reviewed, and is based primarily on the comprehensive international assessment document entitled Atmospheric Ozone 1985: Assessment of Our Understanding of the Processes Controlling Its Present Distribution and Change, to be published as the World Meteorological Organization Global Ozone Research and Monitoring Project Report No. 16.

Watson, R. T.↗
NASA NTRS1986

Preliminary assessment of soil moisture over vegetation

Modeling of surface energy fluxes was combined with in-situ measurement of surface parameters, specifically the surface sensible heat flux and the substrate soil moisture. A vegetation component was incorporated in the atmospheric/substrate model and subsequently showed that fluxes over vegetation can be very much different than those over bare soil for a given surface-air temperature difference. The temperature signatures measured by a satellite or airborne radiometer should be interpreted in conjunction with surface measurements of modeled parameters. Paradoxically, analyses of the large-scale distribution of soil moisture availability shows that there is a very high correlation between antecedent precipitation and inferred surface moisture availability, even when no specific vegetation parameterization is used in the boundary layer model. Preparatory work was begun in streamlining the present boundary layer model, developing better algorithms for relating surface temperatures to substrate moisture, preparing for participation in the French HAPEX experiment, and analyzing aircraft microwave and radiometric surface temperature data for the 1983 French Beauce experiments.

Carlson, T. N.↗
NASA NTRS1985

Seasonal variation of the stratospheric circulation

An extensive analysis is made of the extratropical stratospheric circulation in terms of the seasonal variation of large-scale motion fields, with the aid of height and temperature data obtained from the TIROS satellite. Special attention is paid to a comparison of climatological aspects between the Northern Hemisphere (NH) and the Southern Hemisphere (SH). In order to see the general picture of the annual mach of the upper stratosphere, the zonal mean values of geopotential height of the 1 mb level at 70 deg N and 70 deg S were plotted on the daily basis throughout a year. It is observed that, during the winter, the zonal mean 1 mb height in the NH is much more variable than that in the SH. It is also notable that the SH height is rather oscillatory throughout the longer period from midwinter to early summer. Since the zonal mean height in the polar latitude is a rough measure of the mean zonal flow in extratropical latitudes, the difference of the seasonal variation between the two hemispheres mentioned above is considered to be due mainly to the planetary wave-mean flow interaction in the middle atmosphere. The wave activity in the middle atmosphere is represented more rigorously by the Eliassen-Palm flux associated with vertically propagating planetary waves forced from below. The day-to-day variation of the EP flux in the upper stratosphere shows that the wave activity varies intermittently with a characteristic time scale of about two weeks.

Hirota, I.↗
NASA NTRS1985

Parameterization of the photochemistry of stratospheric ozone including catalytic loss processes

A parameterization has been developed which accurately describes the photochemical response of odd oxygen to dynamically induced perturbations in odd oxygen and temperature. The temperature and odd oxygen dependencies of the loss processes for odd oxygen through catalytic cycles involving odd nitrogen, odd chlorine, and odd hydrogen have been specifically included. The assumption that a linear perturbation equation may be used to describe the response of odd oxygen to perturbations in odd oxygen and temperature has been tested and found to be acceptable for a physically reasonable range of perturbations, i.e., up to approximately 50 percent in odd oxygen mixing ratio and approximately 10 K in temperature. The scheme should prove useful for analyzing the feedback between ozone chemistry and ozone transport and also for analysis of ozone and temperature data.

Stolarski, R. S.↗
NASA NTRS1986

Influence of temperature and hydroxyl concentration on incipient soot formation in premixed flames

Critical equivalence ratios phi(c) have been measured as a function of temperature (1600-1880 K) for premixed flames at atmospheric pressure. The five fuels studied are methane, ethane, propane, ethylene, and acetylene. The flames were stabilized on a flat flame burner and the temperatures were measured using sodium D-line reversal. A linear relationship is found between In phi(c) and 1/T for each fuel. Based on a global kinetic model in which soot precursors are formed by fuel pyrolysis and oxidized by OH, a predictive correlation has been developed which shows the influence of temperature, OH concentration, and C/H ratio on sooting tendency. This correlation describes all of the measured phi(c) versus temperature data, suggesting that the overall mechanism of soot formation is similar among aliphatic fuels.

Harris, M. M.↗
NASA NTRS1986

Composition and stability of the condensate observed at the Viking Lander 2 site on Mars

Surface energy balance and near-surface temperature data from the Viking Lander 2 site taken during the first winter that condensated were observed and analyzed to determine the relative stability of CO2 and H2O frosts. The CO2 frost stability is calculated with an equilibrium surface energy balance model, i.e., the total energy incident on a frost surface is compared with the blackbody energy emitted by the surface. The energy sources considered were IR emission from the atmosphere, sunlight, and the sensible heat flux from the atmosphere. H2O stability was examined as a function of buoyant diffusion and turbulent mixing processes which could remove saturated near-surface gases. The CO2 frost is found to be sufficiently unstable at the time the condensate was observed on the ground, so all CO2 ice deposited at night would boil away in a few hours of sunlight. CO2 ice would not form during a dust storm. Water frost would be stable during the condensate observations, since sublimation would occur at a rate below 1 micron/day. A stable winter thickness of 10 microns is projected for the water ice.

Hart, H. M.↗
NASA NTRS1987

Properties of planetary fluids at high pressure and temperature

In order to derive models of the interiors of Uranus, Neptune, Jupiter and Saturn, researchers studied equations of state and electrical conductivities of molecules at high dynamic pressures and temperatures. Results are given for shock temperature measurements of N2 and CH4. Temperature data allowed demonstration of shock induced cooling in the the transition region and the existence of crossing isotherms in P-V space.

Nellis, W. J.↗
NASA NTRS1986

Field-of-view effects in estimating precipitation from satellite microwave radiances

A one-dimensional cloud model for predicting precipitation is examined. The relation between the averaged brightness temperature and the rainfall rate for various microwave frequencies and field-of-view (FOVs) is studied. The model is utilized to simulate the rainfall rate and brightness temperature data for 19 GHz, a 30 km FOV, 37 GHz, and a combination of IR and microwave data. The data produced by the simulations are described and analyzed.

Adler, Robert F.↗